This invention relates to a novel class of trialkyl thiophosphonates which have been found to possess activity against various insects, and in particular show excellent residual activity against soil-dwelling insects such as Diabrotica.
Some types of trialkyl thiophosphonates are known in the art. U.S. Pat. No. 3,162,570, for instance, describes symmetrical trialkyl tri- and di-thiophosphonates including S,S-di-(n-butyl)-methyl- and -ethylphosphonotrithioates and -dithioates. This patent does not specifically disclose any compounds having an S,S-di(tertiary alkyl) structure.
U.S. Pat. No. 4,258,038 discloses a series of unsymmetrical trialkyl trithiophosphonates in which one alkyl group is a branched C.sub.3 -C.sub.8 alkyl. Such compounds are disclosed as being superior to the symmetrical unbranched alkyls of U.S. Pat. No. 3,162,570, in having equal or better soil insecticidal activity and less phytotoxicity to corn.
It has now been found that certain tri- and di-thiophosphonates having an S,S-di-(tertiary alkyl) structure, show excellent control of insects, especially soilborne insects, including rootworms and cutworms.